Filament wound parts or structures include containers such as tanks, pressure vessels, cylinders and bottles, and conduits such as piping and tubing, which may be used for pressurized or compressed gases and cryogenic gases. Containers for the storage or transportation of such gases may be made with a metal inner liner and a filament wound, structural overwrap made of a composite material formed of high strength, reinforcing fiber within a matrix resin. Further information about fiber wrapped structures may be found in "Composite Cylinders for CNG", 36th Annual Conference, Reinforced Plastics/Composites Institute, The Society of the Plastics Industry, Inc., Feb. 16-20, 1981, Session 22-E, p. 1-8; Morris, E. E., "Advances in Composite Fiber/Metal Pressure Vessel Technology", American Institute of Aeronautics and Astronautics, Inc., 1989, p. 1-9; Morris, V. L., "Advanced Composite Structures for Cryogenic Applications", 34th International SAMPE Symposium, May 8-11, 1989, p. 1867-1876; and Lynn, V., "What is filament winding?", Aerospace Design and Components, September 1986, p. 32-37.
When making filament wound parts or structures, continuous fiber is conventionally wound onto a mandrel in predetermined geometric patterns such as polar, helical or hoop windings, using computerized winding equipment. Creels hold the fiber and it is fed under tension. The mandrel may rotate or be passive. The orientation and thickness of the winding may be selected to match the direction and magnitude of loads in the final part or structure.
As described in U.S. Pat. No. 5,150,812, after the fiber is wound, it may be fused by vacuum bagging and consolidating in an autoclave or directly on the forming mandrel by the application of heat. The mandrel may be thereafter removed.
As exemplified by "Filament Wound Thermoplastic Matrix Pressure Vessels", 32nd International SAMPE Symposium, Apr. 6-9, 1987, p. 662-669, a thermoplastic matrix carbon fiber prepreg may be filament wound using a heat source and a compaction technique to melt the resin and consolidate the plies while winding. As illustrated by other work, when manufacturing parts from a prepreg made from a reinforcing fiber and a thermoplastic resin, heat may be applied from the mandrel to prepreg wound onto the mandrel, and may also be externally applied.
High strength, reinforcing or structural fiber useful in filament winding, includes fiberglass which may be E glass or S glass, and aramid, boron and carbon fiber. The matrix resins are thermosetting and thermoplastic resins. However, thermosetting resins, especially epoxy resins, are the most popular. Conventional filament winding works particularly well with a thermoset matrix material.
Unlike flexible chain, thermoplastic polymers such as polyester or polypropylene, thermoplastic resins having a high melting point, are difficult to process by conventional filament winding techniques. Processing difficulties are accentuated when the filament winding also involves a structural fiber.
Therefore, there is a need for an improved filament winding process for forming a consolidated, filament wound composite from reinforcing fiber and a thermoplastic matrix material having a high melting point.